NL8602904A - METHOD AND APPARATUS FOR PYROLYTIC COATING OF GLASS. - Google Patents

Description

- 1 - * * IJL 33.765-Vo / voïl

Method and device for pyrolytic coating of glass »

The invention relates to a pyrolytic coatinys method, in which a hot glass substrate in sheet or hand form moves in a downstream direction under a coating chamber which is opened down to the substrate and in which a coating of coating precursor material is formed on the surface of the substrate. The invention further relates to a device for pyrolytically forming a metal compound coating on a surface of a hot glass substrate in plate or hand form, with a transit means for transporting said substrate along a path in a downstream direction, a roof trick wall, which forms a coating chamber, which is opened downwards to the track, and a means for delivering a coating precursor material into the chamber.

Such an apparatus and methods are useful in the manufacture of coated glass for various purposes, the coating being selected in view of some special desirable properties on the glass. Particularly important examples of coatings that can be applied to glass are those which are designed to reduce the emissivity of the coated surface with respect to infrared radiation, in particular infrared radiation with wavelengths above 330 µm and those designed to reduce the total energy transmission of the coated glass 25 with respect to solar radiation. For example, it is known to provide glass with a tin dioxide coating of low infrared emission for heat insulation purposes, and it is also known to provide glass with a metal oxide-reducing coating of the solar energy transmission, such as titanium dioxide or a mixture of metal oxides, such as ^ e2 ° 3 + Co ° + Cr2 ° 3 with a main objective of reducing the absorption of solar heat or glare.

It is clear that coatings applied to glass used for glazing purposes must have a high and uniform optical quality and that they must be durable. It is also clear that the coating formed must have the correct thickness for the purpose in question and that it is commercially desirable that the rate of formation of the coating material should be sufficient to build up the desired coating thickness, even when the substrate with a moves at fairly high speed, such as may be imposed by other processes in the manufacturing cycle.

It has been found that various factors related to the coating process affect the manner in which the coating is formed on the substrate and from these the physical phase of the material from which the coating is formed and the nature of this material can be mentioned as well as the energy with which the material comes into contact with the substrate and the temperature of the coating chamber and of the substrate to be coated.

For example, it is known that the rate at which coating reactions take place is temperature dependent. Generally, the higher the temperature, the faster the coating formation rate is, while the crystal structure of the coating formed is also finer. A uniform fine crystal structure is advantageous for a high coating quality and for durability.

Consequently, prior art has attempted to check the temperature of the hot substrate prior to coating formation, while steps have also been taken to control the temperature of the entire environment in the coating chamber.

The present invention is based on the insight that the coating quality is strongly influenced by a factor which has hitherto been overlooked, namely the temperature of the atmosphere immediately above the substrate in the zone, where the formation of the coating is starts.

As a result, the present invention provides a pyrolytic coating method, in which a hot glass substrate in sheet or hand form moves in a downstream direction under a coating chamber, which is opened down to the substrate and in which the surface of the substrate is 1602904. - A coating is formed from a coating precursor material immediately, characterized in that the gaseous environment in the immediate vicinity of the surface of the substrate, at least in the zone where such formation of the coating begins, is controlled by preheated gas in conducting a downstream direction into the chamber to penetrate the chamber in contact with the substrate and to form a coating layer covering the substrate at least as far as this zone.

The possibility of controlling the gaseous environment, which is in contact with the substrate in the zone, where coating formation begins, is a factor that has been overlooked so far. It has been found that it is easier to control the conditions in such a coating with the required degree of accuracy than it is to control the entire environment within the coating chamber and thereby it is possible to form a general gas flow, which is from upstream of the zone where the formation of the coating begins, comes into contact with the substrate in such a way that a microclimate is present at this zone, which is in contact with the surface of the substrate, which climate is favorable for the coating reactions that will take place. In order to accomplish this, it is necessary to control or modify the atmospheric layer, which would normally be entrapped in the coating chamber in contact with the substrate, by the preheated gas supply, in order to advantageously coat the glass to condition for the coating reactions. This is in particular a difference from the prior art, in which the naturally trapped gas layer is disrupted by directing strong flows of relatively cool gas onto the substrate at the upstream end of the coating chamber. Moreover, since it is relatively easy to control the conditions within the coating layer, it is relatively easy to adjust these conditions, eg to accommodate minimal variations in the thickness of the coating deposited over a continuous production run. - 8602904 - 4 - ί ί

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to retire.

Embodiments of the invention, in which a generally downstream flow of coating precursor material above the coating layer is contained within the coating chamber 5, are particularly advantageous for the formation of high quality coatings, namely because of the control thus obtained. exerted on the flow of reaction products within the atmosphere of the coating chamber.

Preferably, at least in part, a generally downstream flow of gas through the coating chamber is maintained by aspirating atmospheric material from this chamber at its downstream end. To the extent that the downstream flow is maintained by means of exhaust forces generated in exhaust pipes at the downstream end, the forces acting on the gas at the upstream end of the coating chamber and the forces which are exerted by the gas flow at the upstream end of this chamber are more diffuse. It has been found to promote the onset of a coating substrate with a fine and uniform crystal structure at the upstream end of the coating chamber. The crystal structure of the coating at the glass / coating interface strongly influences the manner in which the rest of the coating thickness is built up as the substrate moves through the coating chamber and is extremely important in the formation of high quality coatings.

A method of the present invention provides the greatest advantages when performed within an at least substantially closed coating chamber, thereby avoiding disruption of the coating by random flows. In fact, the downstream end of the coating chamber is the most likely source of such random flows. As a result, in particularly preferred embodiments of the invention, the coating chamber is substantially closed at its downstream end so as to allow an exchange of atmospheric material between the downstream end of the coating chamber and a further downstream region of the coating chamber. substrate web. Such a seal can be effected, for example, by an exhaust pipe extending over the entire width of the coating chamber at its downstream end. This achieves the advantage of avoiding any dilution or contamination of the atmosphere in the downstream end of the coating chamber from the downstream downstream region and also prevents currents from the coating chamber atmosphere from interfering with any further treatment of the substrate and depositing any unwanted additional material on the coating downstream of the coating chamber.

In particularly advantageous embodiments of the invention, the glass substrate comprises a properly formed hot glass belt, the coating being formed after the belt exits a belt former and before it enters a softening lehr. The coating chamber can thus be located in a place where the glass already has a temperature suitable for the pyrolytic coating reactions to take place, so that costs associated with reheating the glass to such a temperature are avoided or considerably reduced. . It is also important that the coating takes place in a chamber which is physically separated from the band-forming device on one side and the softening lehr on the other side. If no such separation exists, and it is common in known prior proposals in this field that the coating takes place within the narrowness of the softening lehr, the atmospheric conditions within the coating chamber may be disturbed by gas streams flowing from the softening lehr and from the banding device flows - such flows often carry dust and other contaminants, which can be included in the coatings as errors - and there will also be a risk of disturbing the pattern of atmospheric flows in the lehr, which would lead to less favorable softening conditions.

Depending on the pressure conditions above and below 8602904 Γ ί

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- 6 - substraat The substrate in the coating chamber may have a tendency for the atmosphere to flow from below the substrate upward along its sides, contaminating the precursor atmosphere above the substrate. This can lead to the formation of coating deposits, which are thinner at the edges of the substrate than at the central part of the substrate, with the result that a certain part of the width of the coated substrate has an unacceptable quality. . On the other hand, there may be a tendency for the precursor atmosphere to flow beneath the substrate, where it may deposit and undesirably coat on the bottom surface thereof. Depending on the flow pattern of the atmospheric flows in and under the coating chamber, this undesired coating can be more or less regular, but so thin that extremely objectionable interference effects occur, eg a more or less regular coating, the thickness of which is the direction of the center of the substrate decreases, or a rather irregular coating with a pattern, which some people compare to the pattern on a backgammon game board. In order to reduce these disadvantages, special preferred embodiments of the invention are characterized in that over at least a part of the length of the coating chamber, a flow of atmospheric material 25 beyond the side edges of the substrate and between zones vertically above and vertically below the substrate is countered. It has been found that by proceeding in this way the properly coated width can be increased and this is especially valuable when coating a newly formed continuous glass tape.

It has been found that the manner in which the coating precursor material is introduced into the coating chamber is not critical to the quality of the coating, so that it can be introduced e.g. into the vapor phase.

Preferably, however, a coating precursor solution is sprayed down and downstream.

This simplifies the release of coating precursor material, while also minor disruption of the coating layer 8602904. . * s - 7 - is caused because evaporated material already has some impulse in the downstream direction. It also extends the path of the sprayed material compared to vertical spraying from the same height, allowing more time for the sprayed coating precursor material to be conditioned in the coating chamber prior to contact with the substrate.

It is preferred when a coating precursor solution is sprayed down into the coating chamber and through the coating layer, since this involves handling the large amounts of coating precursor material required to form thick coatings, especially on fast-moving substrates, greatly simplified. The invention can thus be adapted to form coatings of a fairly great thickness, eg, thicknesses of 500 nm and more.

It is known that certain disadvantages are associated with the known liquid phase coating techniques. In such known techniques, it is very difficult to avoid contamination of the formed coating due to splashing of the sprayed droplets when they collide with the substrate. Also, when conventional liquid phase coating techniques are employed, contact between the generally fairly large amounts of the sprayed coating solution and the hot substrate can cause significant difficulties, especially when the coating is deposited on a newly formed hot glass strip because it influences subsequent hardening treatment. The result of this is that the glass is softened poorly, and in some cases residual stresses trapped in the glass ribbon make it more difficult to cut, which may even be such that the glass breaks when cut into plates.

In order to reduce or eliminate these problems, some preferred embodiments of the invention provide a method of heating a spraying zone of the coating chamber to cause evaporation of a portion of the coating precursor material before it reaches the substrate to provide the atmosphere in this 8602904 *> - 8 - zone to be provided with evaporated coating precursor material; that the solution is sprayed with sufficient energy to ensure clear contact between the remaining sprayed coating precursor material and the substrate, in order to begin the coating of the substrate surface, with the atmosphere provided with vapor phase coating precursor material in the downstream direction from the spraying zone along and in contact with the coated substrate surface for a contact time of at least 10 seconds, after which any residual material from the precursor flow is directed away from the substrate.

Using this, it is possible, at a given precursor release rate, to reduce the strength of the currents that collide with the glass at the area where coating formation begins. This is especially important in reducing the disturbance of a coating layer of the atmosphere in contact with the substrate, and this can lead to the formation of a very high quality coating. It has been found that a relatively small amount of the released material can penetrate the coating layer and collide with the glass, so that the coating layer can remain largely undisturbed.

Such a method is useful in forming coatings with low and uniformly low turbidity. This is particularly surprising since it has hitherto been considered necessary to remove the coating precursor and reaction product vapors from the substrate as quickly as possible - contact times of between 2 and 5 seconds in known processes - namely to avoid the risk of false deposits, which would lead to an increase in turbidity, from these vapors.

The reasons why such a process produces better coating quality are not entirely clear. One possible explanation is that a significant portion of the thickness of the precursor material coating is vapor phase while the substrate moves through the passage portion of the coating chamber. Vapor phase deposition 8502904-9m techniques are known to promote a fine and uniform crystal structure in the coating. But this does not explain why the use of a method according to the invention results in the formation of a coating, which has a much more regular thickness than can be obtained by using conventional vapor phase deposition methods. Another possible explanation is that although only a small portion of the coating thickness can be attributed to vapor-phase deposition, conditioning of the newly formed main body of the coating takes place during said contact time of at least 10 seconds, during which the substrate is exposed to the coating precursor vapor so that the crystal structure of the coating can be changed in a manner that is beneficial to the coating quality and in particular that exposing the newly formed coating to the precursor vapor allows any small pores in the coating can be filled, resulting in a harder and more compact and weather resistant coating.

The present invention can advantageously be combined with the invention described in British patent application 85.31423, which application relates to a method for pyrolytically forming a metal compound coating on a surface of a hot glass substrate in sheet or hand shape, while this in a downstream. upwardly along a path through a coating chamber in which at least one flow of a coating precursor solution is sprayed down to the substrate, characterized in that a spraying zone of the coating chamber is heated in order to evaporate part of the coating precursor material cause it to reach the substrate to provide the atmosphere in this zone with evaporated coating precursor material; that the solution is sprayed with sufficient energy to ensure clear contact between the remaining sprayed coating precursor material and the substrate, in order to begin the coating of the substrate surface, the atmosphere being provided with vapor phase coating precursor material, 8602904-10 - * *

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is guided downstream from the spraying zone along and in contact with the coated substrate surface for a contact time of at least 10 seconds, after which any residual material of the precursor flow is directed away from the substrate.

According to other preferred embodiments of the invention, to form a metal oxide coating, coating precursor material and an oxidizing gas are continuously fed into a mixing zone, wherein the precursor material and the oxidizing gas are brought together out of contact with the substrate and subjected to mixing forces to provide a atmosphere containing an intimate mixture of precursor vapor and oxidizing gas, a flow of such mixture being continuously fed from this mixing zone into and along a passage to which the substrate surface is exposed.

This also reduces disruption of the coating layer by the released coating precursor material.

In fact, it is quite surprising that the gas coating layer 20 above the substrate does not act as a screen, preventing such a vaporized atmosphere from forming a coating on the glass. But in this way a very high quality coating can be formed, probably because the coating precursor vapor can mix with the coating layer without disturbing its general flow.

It is particularly surprising that such mixing does not affect the premature formation of coating reaction products, which would flow along the passage above the substrate and cause false deposits, which would indicate errors on or in the coating. It is also surprising that the formation of an intimate mixture of the coating precursor and an oxidizing atmosphere within the mixing zone and then causing this mixture to flow along the passage in contact with the substrate is sufficient to obtain a coating, at least virtually free. is of unpredictable thickness variations and that the exact manner in which the coating precursor material is introduced into the coating chamber is not critical to obtaining such a regular thickness. to note that, contrary to what may be expected, such a mixture in fact leaves sufficient unreacted coating precursor material available for the formation of a coating on the substrate when this material is vapor phase down along the passage flows. This is quite different from the known from the prior art in this field.

In any event, it has been found that such preferred embodiments of the present invention simplify the formation of coatings of a high and uniform quality and allow the formation of these coatings with a more regular thickness than previously possible.

Such embodiments of the invention also provide special advantages in the formation of relatively thick coatings, e.g. coatings above 400 nm thick. It has been found that rapid removal of the vaporized atmosphere is not a prerequisite for a substantially error-free coating, so that more time is available to build up a coating to a desired thickness.

For example, the present invention can be advantageously combined with the invention described in British patent application 85.31424, which application relates to a method for pyrolytically forming a metal oxide coating on an upper surface of a hot glass substrate in sheet or hand form during its transport in a downstream direction along a path leading under a downwardly open coating chamber, wherein the coating is formed by a coating precursor vapor and an oxidizing gas supplied in the downstream direction through a passage of the coating chamber , to which the substrate surface is exposed, characterized in that the coating precursor material and the oxidizing gas are introduced into a mixing zone of the chamber in or next to the upstream end of the passage, heat energy is supplied to the mixing zone and the precursor material and 8602904-12 - Ê * t the oxid The respective gas is intimately mixed in the mixing zone, while being exposed to the substrate, but at such a height that the formation of the coating starts from an at least substantially homogeneous vapor mixture and ensuring that this mixture is continuously passed through the passage into contact with the top surface of the substrate flows.

Preferably, the gas forming the coating layer is preheated to a greater degree than is possible due to the heat transfer only from the substrate. It has been found that it is particularly advantageous for a high and uniform coating quality that the temperature of the gases in the coating layer is high in order to provide the best possible conditions for the start of coating formation. This also promotes rapid coatings formation.

One of the problems, which has been the subject of much research, concerns the variations in the thickness of the coating over the width of the substrate to be coated. As a characteristic of this problem, it has been found that when a newly formed flat glass strip is coated, the edges of the strip are coated less thick than a central strip strip. As a result, these peripheral areas do not meet the desired quality standards and are considered waste.

The contamination of the coating precursor material at the sides of the coating chamber has already been pointed out as a possible cause of this phenomenon. Recent research has led to the conclusion that this is also the result of temperature differences over the width of the substrate to be coated. For example, it is known that material in the coatings chamber will cool faster the closer it is to the side walls of the chamber.

In a preferred embodiment of the invention, the gas which forms the side edge regions of the coating layer is preheated to a greater extent than at the center. As already noted, there is a natural heat loss through the sidewalls of the coating chamber and any passage leading to this chamber, applying the aforementioned feature a thermal barrier 8602904

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- 13 - which allows the compensation of heat loss. As a particular example of the benefits to be achieved which can be obtained by applying this preferred embodiment of the present invention, it has been found that when a newly formed hot glass tape is coated even when the glass enters the coating chamber with a at least substantially uniform temperature profile across the width, in the absence of a specific control of the atmosphere in contact with the tape at the zone where the coating starts, one-sixth of the tape at each side edge can be of unacceptable quality, so that a third of the total bandwidth is only suitable as glass waste. The use of this feature has shown that the usable coated width can increase and, under optimal operating conditions, the useful product yield is not so much limited by the quality of the coating at the tape sides as by the quality of the glass itself. location of these edges. It should be borne in mind here that due to various factors a few centimeters at each edge of the glass tape have an irregular and unacceptable optical quality and in any case must be removed or used as glass waste.

Preferably, the coating layer gas is heated at least above the side edges of the substrate to a temperature greater than that of the underlying edge regions of the substrate. This results in the formation of a coating with an improved optical quality and durability and a better thickness uniformity, at least at the edges of the substrate, and this promotes the compensation of the heat loss through the side walls.

Preferably, the gas for forming the coating layer enters the upstream end of the coating chamber from an adjacent pre-chamber. This is a very simple way of ensuring the formation of the coating layer from gas covering the substrate, which layer can then be carried by the substrate to move in contact therewith at least to the zone where 8602904 is * - 14 - the formation of the coating begins. The upstream end of the pre-chamber is preferably at least substantially closed, in order to prevent the flow of gas in this pre-chamber from upstream, eg from a belt-forming device, and to create a buffer zone, from which gas can be supplied in order to maintain the coating.

Preferably, the preheating of the gas is performed at least in part in the pre-chamber and from above the level of the substrate. This simplifies direct control of the temperature of the gas entering the coating chamber from the pre-chamber.

Gas in the pre-chamber can be heated there in any suitable manner, but preferably preheating of the gas in the pre-chamber is accomplished by means of burners, as it is considered to be the most efficient and since this provides simple and accurate control of the heating permits, with a quick response to any adjustment of the heating controls.

It is advantageous when the preheated gas is blown up to the sides of the pre-chamber from below the level of the substrate. This promotes the compensation of side heat losses at the level of the substrate, while it has an advantageous effect on the atmospheric conditions present in the pre-chamber above the substrate, especially as it tends to prevent cold air from passing through the side walls from the front room.

On the other hand, or additionally, some particularly preferred embodiments of the invention are characterized in that the preheated gas is blown downstream into the antechamber from above the level of the substrate. This has been found to promote a downstream flow of gas into and through the coating chamber and is particularly advantageous in embodiments of the invention where the pre-chamber is not closed at the upstream end.

On the other hand, or additionally, it is advantageous if the preheated gas is blown down into the pre-chamber and that this gas is prevented from flowing down the side edges of the substrate. This is another convenient way of introducing preheated gas into the pre-chamber to control atmospheric conditions above the substrate.

It has already been pointed out that it is desirable to exercise control over the temperature of the gas-coating layer, in particular to compensate for the heat losses through the side walls of the coating chamber. As an alternative, or additional, way of effecting such compensation, according to some preferred embodiments of the invention, the volume flow of the gas forming the coating layer is controlled differentially across the width of the substrate.

It is advantageous if atmospheric material is maintained in a generally downstream flow over a substantial portion of the height of the chamber, in part by directing a gas flow into the chamber in the downstream direction. This is particularly advantageous in promoting a generally downstream flow of atmospheric material within the coating chamber, while maintaining the atmospheric pressure in the chamber at such a level that there is little or no suction of external atmospheric material into the chamber through any openings in the walls, e.g. due to suction at the downstream end thereof.

Preferably, at least one auxiliary preheated gas stream is introduced into the coating chamber to flow in or downstream of the coating layer and through the zone where coating formation begins.

Such an auxiliary gas flow has the advantage of increasing the downstream flow impulse of the cover layer, and / or protecting it from arbitrary flows within the chamber. The use of such a flow also enables relatively fine control of the temperature and / or the flow rate of the coating layer as a whole.

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A particularly important application for a method according to the invention is present in the formation of tin oxide coatings, which use stannous chloride as the coating precursor material. Tin oxide coatings, which reduce the emissivity with respect to long-wavelength infrared radiation from the surfaces of glass plates to which they are applied, are widely used to reduce heat transfer from glass-lined structures. This is of course only one example of an application for which the method can be used. As another example, the method can be used in the formation of a coating of titanium dioxide, or a coating of a mixture of oxides, such as a mixture of cobalt, iron chromium oxides.

The invention also relates to a device for pyrolytically forming a metal compound coating on a surface of a hot glass substrate in plate or hand form, with a conveyor for transporting said substrate, along a path in a downstream direction a roof structure, which forms a coating chamber, which is opened downwards to the track and a means for delivering a coating precursor material into the chamber, characterized in that a pre-chamber, which is connected in communication 25, is arranged upstream of the coating chamber with the coating chamber through an entrance slot, which is partially defined by the path of the substrate and through which gas can flow into the coating chamber, to form (when the device is in operation) a coating layer covering the surface of the substrate along a first part 30 of the length of this chamber and that a means for controllable preheating is provided of the gas that forms the coating.

Such a device is particularly suitable for forming a high quality, regular thickness coating in a continuous process, eg in a process as described above. The device can be placed at any suitable location. Such an arrangement is particularly advantageous because it allows the control of conditions at the zone where coating formation begins, which conditions are otherwise difficult to change.

Advantageously, the exhaust pipes are provided with one or more inlets at the downstream end of the coating chamber. Exhaust pipes placed there are extremely advantageous for generating suction forces acting on the gas at the upstream end of the coating chamber, in order to maintain a generally downstream flow of the material into the coating chamber while ensuring that there is no dead zone within the chamber where the corrosive precursor material or reaction products can accumulate and that the forces exerted on the atmosphere at the upstream end of the chamber will be fairly diffuse. This has been found to reduce the disturbance of the atmospheric flows present in the upstream end of the coating chamber.

In a particularly preferred embodiment of the invention, a curved outlet vane is provided which extends over at least the major portion of the substrate web at the downstream end of the coating chamber, which vane partially forms at least one outlet pipe inlet. Such a device has a simple construction and can be easily placed. The use of a curved vane is particularly valuable in the uniform flow of material to be extracted into the exhaust pipe inlet and aids in avoiding negative pressure waves there, which could disturb atmospheric flows in the passage. It is particularly desirable to use such a blade which extends over the entire width of the coating chamber and which is adjustable in height above the substrate web, eg by means of a swivel mount, in order to maximize the downstream end closure from the coating station.

In particularly preferred embodiments of the invention, a boundary wall is disposed 8602904-18 above the substrate web, which extends and at least substantially closes the entire width of the downstream end of the coating chamber. Such a boundary wall can for instance be formed at least in part by a said outlet vane. This is a very simple way of ensuring that changes in conditions immediately downstream of the coating chamber end will not directly affect the conditions in the coating chamber and vice versa.

In particularly advantageous embodiments of the invention, the coating station is disposed between the exit of a tape manufacturing device and the entrance to a softening lehr. When this is done, it appears that the glass can reach the coating station with a temperature equal to, or nearly equal to, the temperature required for the pyrolytic coating reactions to take place. As a result, the application of this feature eliminates the need for further heating devices, as would be necessary to raise the temperature of the glass to be coated from the room temperature.

It is advantageous if an element is arranged over at least a part of the length of the coating chamber for preventing a flow of atmospheric material beyond the sides of the substrate web and between zones vertically above and vertically below this web.

Such an undesirable flow of atmospheric material could cause an irregular deposition of coating material on the top and / or bottom surface of the substrate, especially at the side edges thereof.

It is particularly preferred that the coating precursor material dispenser is positioned such that liquid coating precursor material is sprayed down and downstream. This is a very simple device for dispensing relatively large amounts of the coating precursor material, as may be required in the formation of fairly thick coatings, and allows such release without disturbing a general flow of atmospheric material through the coatings. 8602904 * · * - 19 - chamber downstream, as is advantageous for forming high quality coatings.

In such embodiments, it is particularly preferred when the sprayer is arranged to spray the coating precursor solution into a spraying zone of the coating chamber from a height above the substrate web of at least 75 cm, that a heating member is provided for supplying heat to the spraying zone, the roof structure forming a passage portion of the coating zone leading downstream of this spraying zone and providing the coating chamber with a total length of at least 2 meters, while a means is provided for generating aspiration forces on atmospheric material within such a passageway to cause such material to flow along the substrate web to the downstream end of the passage and enter an exhaust pipe to carry such material away from the substrate web.

A device with these features is particularly useful. Such a device is more economical in its use than the conventional vapor coating device, in which all of the coating precursor material must be evaporated prior to contact with the glass, and the present device can be constructed more simply than the known spraying device, in particular because of the problems associated with splashing and taking large amounts of the sprayed coating precursor solution from the zone where the coating is formed can be easily prevented by ensuring that the heat released is sufficient to cover a substantial portion of the sprayed coating precursor.

When such an arrangement is used, it has been found to be easier to reliably and reproducibly form coatings of high optical quality and uniform structure even at high coating formation rates and without inducing high thermal stresses in the glass. In particular, it has been found to be easier to form coatings with low, and uniformly low, turbidity.

8602904 * · * "- 20 -

Of course, in order to achieve such reproducible high coating quality, the device must be properly applied, but the combination of device features, as described above, is particularly advantageous for simplifying the control of conditions within the coating chamber. In order to obtain these good results, it has been found that when using the device, it is best to control the conditions such that a substantial portion of the coating precursor solution is evaporated before it penetrates the coating layer to contact the substrate. so that the coating is not largely disturbed by the sprayed material and so that the atmosphere within the spraying zone is supplied with a coating precursor vapor, which is then extracted through the passage, where it remains in contact with the substrate.

Heretofore, it has been deemed necessary to deliver the precursor solution from close to the substrate, a spray height of 30 cm or less is common, so as not to give the precursor material time to react with the atmosphere within the coating chamber and to form reaction products which could be deposited on the substrate and form errors on the coating.

It was also considered necessary to aspirate abundant precursor coatings and reaction products from the substrate as soon as possible, again to prevent false deposition on the substrate and coating zone lengths of 60 cm to 100 cm are typical of the prior art.

The reasons why the use of such a device according to the invention provides better coating qualities are not entirely clear, but the fact remains that with the aid of such a device it is possible to produce coatings with a uniform and less turbidity than hitherto. was possible. The coatings 35 formed can have a high optical quality, as well as a regular and predictable thickness. Moreover, the use of such a device makes it possible to form these coatings more quickly on glass substrates, so that greater thicknesses can therefore be achieved or applied to faster moving substrates than has been possible until now.

In fact, this represents a radical break with the prior art leather and is the subject of the invention, which is described in British patent application 85.31423, which application relates to a device for pyrolytically forming a metal coating. bond coating on a surface of a hot glass substrate 10 in plate or hand form with a conveyor, for conveying said substrate in a downstream direction along a track, a coating station with a roof structure, which forms a coating chamber, which is down to the web is opened and a means for spraying a coating precursor solution downwards into the substrate in this chamber, characterized in that the spraying means is arranged to spray the coating precursor solution in a spraying zone of the coating chamber from a height above the sub street track of at least 75 cm, which has a heating member for supplying war at the spraying zone, the roof structure forming a passage portion of the coating chamber, which leads downstream of this spraying zone and provides the coating chamber with a total length of at least 2 meters, while a means is provided for generating extraction forces on atmospheric material within a such a passageway, to cause such material to flow along the substrate web to the downstream end of the passageway and to enter an exhaust pipe to carry such material away from the substrate web.

According to some highly preferred embodiments of the invention, the coating chamber has a passageway through which coating precursor vapor and an oxidizing gas can be passed downstream in contact with an upper substrate surface during the transport of the substrate and in which an element is provided, defining a mixing zone in which the coating precursor material and the oxidizing gas may be combined and contacted in a non-contact manner with the substrate to form an atmosphere comprising an intimate mixture of the precursor vapor and the oxidizing gas, which mixing zone communicates with the passage to allow flow of such a mixture to flow through the passage from the mixing zone.

Such a device is particularly suitable for the formation of coatings; of high quality, which are at least practically free from unpredictable thickness variations at coating formation rates and in a continuous process.

This again allows a reduced perturbation of the coating layer by the released coating precursor material, while using this device can produce a very high quality coating, probably because the coating precursor vapors are formed at least substantially without the general flow. with the 15 coat can mix.

As an example of such embodiments, a device according to the present invention can also advantageously use one or more features of the device according to British patent application 85.41324, which application relates to a device for use in the pyrolytic formation of a metal oxide coating on a top surface of a hot glass substrate in plate or hand form, with a conveyor for transporting said substrate in a downstream direction along a track and a roof structure, which forms a coating chamber, which is opened down to the track and with a passage , through which a coating precursor vapor and an oxidizing gas can be passed downstream into contact with the top surface during the transport of the substrate, characterized in that the roof structure in or adjacent the upstream end of the passage defines a mixing zone, which to the runway that an organ aa is present for injecting coating precursor material into the mixing zone from a height of at least 50 cm above the level of the substrate web and that means is provided for injecting oxidizing gas into the mixing zone, in which the coating precursor material and the oxidizing gas can be brought together, mixed and heated to form an atmosphere containing 8602904-23 - an intimate mixture of precursor vapor and oxidizing gas, which mixing zone communicates with the passage to allow flow of such atmosphere through the passage from the mixing zone possible.

It is particularly preferred when the roof structure in the downstream direction has a marked height reduction above the substrate web so that the downstream flow of atmospheric material from the coating precursor material delivery zone is throttled in the coating chamber. The use of this feature allows for a relatively high upstream release zone, to provide sufficient space for good mixing of the released coating precursor material into the atmosphere within this zone and which can serve as a reservoir of coating material vapors, which are then forced will flow down toward the substrate to mix with the coating and flow downstream of the coating chamber as a concentrated and uniform flow which is advantageous for the formation of coating material from the vapor phase.

Preferably, the gas preheater is controllable such that it heats the different gas-forming portions of the coating layer to varying degrees across the width of the substrate web. This allows a finer 2.5 control of the temperature of the gas that will form the coating.

It is advantageous that the gas preheater is controllable such that it heats the gas-forming side edge regions of the coating layer to a greater degree than the gas-forming central portions of the layer. This is particularly advantageous in providing compensation for the increased cooling of the atmosphere within the coating chamber, which takes place next to the side walls of this chamber, in order to coat a wider strip of the substrate up to a desired promote thickness.

In preferred embodiments of the invention, the divider above the entrance slot has a port for adjusting the opening of the entrance slot. This provides a further means for controlling the conditions in the coating layer of the gas flowing into the coating chamber, eg for varying the velocity of such gas flow, to provide an adaptation to prevailing conditions under the release zone of the coating precursor material.

Preferably, the gate is provided with independently movable sections for differential adjustment of the input slot across the width of the substrate web, so that such a control can be effectuated independently at different locations across the width of the substrate web, eg after detection of thickness variations in the formed coating.

In particular the. In preferred embodiments of the invention, a means is provided for heating the atmosphere in the antechamber from above the level of the substrate web. This is a very simple device for directly influencing the temperature of the coating layer of the atmosphere in contact with the top surface of the substrate in the pre-chamber.

It is advantageous if this pre-chamber heater includes burners, as it allows for a very efficient heating effect, as well as easy adjustability and a quick response to any adjustment.

Preferably, a means is provided for blowing preheated gas into the pre-chamber. This allows the gas to be blown into the pre-chamber without or with a reduced heat loss to a substrate therein, and this means that an adequate supply of gas to form the coating can be provided from a smaller pre-chamber.

Advantageously, means is provided for blowing pre-heated gas from below the level of the substrate web up to the sides of the pre-chamber.

35 This is a very convenient and efficient device for compensating for the heat loss through the side walls of the pre-chamber.

Preferably, a means is provided for blowing preheated gas downstream of the substrate web from above the level of the substrate web in the downstream direction.

This is another convenient way of blowing pre-heated gas into the pre-chamber and has the added benefit of promoting generally downstream flow of gas into and through the coating chamber.

According to some preferred embodiments of the invention, a means is provided for blowing preheated gas down into the pre-chamber and preventing this gas from flowing down the side edges of the substrate web. This is a further convenient way of blowing pre-heated gas into the pre-chamber, in order to control the atmosphere immediately above the substrate web.

According to other preferred embodiments of the invention, the pre-chamber has a roof which slopes down towards the top of the entrance slot. This promotes a regular flow of gas into and through the entry slot to form the cover layer in contact with a substrate on the web.

It is advantageous when a means is provided for directing a gas stream downstream into the chamber to maintain a generally downstream flow of atmospheric material over a substantial portion of the height of the chamber. Such an organ aids in maintaining atmospheric pressure within the coating chamber, thereby reducing the likelihood that arbitrary air flows into the chamber will occur through its walls, where they would disrupt the desired pattern of atmospheric flows, while avoiding such In general, downstream flow also aids in keeping the atmosphere coating layer down against the substrate.

Preferably, a means is provided for delivering into the coating chamber at least one auxiliary stream of preheated gas to flow in or downstream of the coating layer and through the zone where coating formation begins. Here, an auxiliary gas stream can be generated in order to strengthen and / or protect the coating layer against any arbitrary flows that may be present in the chamber. The use of such a flow also enables relatively fine control of the temperature and / or the flow rate of the coating layer as a whole.

The invention will be explained in more detail below with reference to the drawing, which shows a number of preferred embodiments of the device according to the invention and with reference to examples of some methods according to the invention, which have been carried out with such devices.

Figures 1 to 3 each show a cross-section through an embodiment of the device according to the invention and Figure 4 shows a cross-section along the line IV-IV in Figure 3.

FIGURE 1

In Figure 1, an apparatus for pyrolytically forming a metal compound coating on an upper surface of a hot glass substrate 1 in sheet or hand form, with conveyors, such as rollers 2, for conveying the substrate in a downstream direction 3 along a track, which is designated by the reference numeral 1. The track 1 extends through a coating station 4 with a roof structure 5, which defines a coating chamber 6, which is opened downwards towards the substrate track 1 and a spray nozzle , which is schematically indicated at 7, for spraying a flow of a coating precursor solution into the chamber 6, in a direction 8, down toward the substrate 1.

The spray nozzle 7 is positioned such that it sprays the coating precursor solution stream into a spray zone 9 of the coating chamber 6. In the embodiment shown, the spray nozzle 7 is placed such that it sprays the coating precursor material from at least 75 cm and preferably at least 1.2 meters above the substrate web 1 and consists of a type known per se. The nozzle is positioned so that it sprays the coating precursor solution in the direction 8602904 - 27 - 8, which leads down towards the substrate 1, as well as downstream 3, and is movable back and forth along a (not shown) web transverse to the width of the substrate web.

In the shown embodiment a heating element is arranged for supplying heat to the spraying zone. Such a heating means comprises downwardly directed radiant heaters 10, which are arranged in the roof of the spraying zone 9. A pipe 11 is provided for delivering a flow of preheated gas into the spraying zone 9 in a direction which directs the sprayed flow 8 of the coating precursor material. The outflow nozzle 12 of the pipe 11 is positioned at the top half of the height between the spray nozzle 7 and the substrate 1 and is arranged to release the gas stream from upstream of the coating precursor spray delivery axis. The outflow nozzle 12 has a smaller width than the substrate web 1 and is moved back and forth through the spray zone together with the spray nozzle 7. The gas released from the mouth 12 initially has at least substantially a horizontal direction directed transversely of the transverse path of the droplet flow 7, in order to maintain a circulation of gas within the spraying zone 9.

The delivered gas is preferably preheated, e.g. to an average temperature in the range of 300 to 600 ° C, and air is suitable, for example. The heaters 10 cause the evaporation of part of the flow of sprayed droplets during their movement towards the substrate 1 and the vapor thus formed is entrained in the flow of preheated air, which is released from the mouth 12.

The roof structure 5 forms a passage portion 13 of the coating chamber 6, which leads downstream from the spraying zone 9 and provides the coating chamber 6 with a total length of at least 2 meters and preferably a length of at least 5 meters. In the embodiment shown, the roof structure 5 comprises a bridging wall 14 above the substrate web, which is directed at least substantially vertically downwards, so as to form an outlet slot 15 at the location of the 3602904-23. * downstream end of the spray zone separating this zone from the passage, while the passage 13 has a height which decreases downstream from a maximum value at the outlet slot 15. The height of the outlet slot 15 is less than half the height between the spray nozzle 7 and the substrate 1.

At the downstream end of the passage 13, atmospheric material is extracted into exhaust pipes 16, which have an inlet 17, which is partly formed by a curved exhaust vane 18 extending over the entire width of the passage above the path of the substrate 1 and at least substantially closes its downstream end, so that the flow of atmospheric material into or out of the coating chamber 6 at the location of the downstream end of the passage 13 is at least substantially prevented. Such a blade 18 may optionally be pivotally mounted so that it can be adjusted for a minimum distance from the substrate 1. At the location of the downstream end of the passage 13, atmospheric material is also extracted into side exhaust pipes 19, which are on either side of the coating chamber are arranged to prevent lateral spreading of the atmospheric material flowing through the coating chamber.

In fact, such side exhaust pipes 19 extend at least substantially the entire length of the passage into the spraying zone and substantially upstream of the upstream end thereof, in order to prevent the flow of coating precursor vapors below the substrate web 1.

The coating station 4 is disposed between the outlet of a belt-forming device (not shown), eg a float tank and the entrance to a softener 20.

A passage from the tape-forming device to the coating chamber 6 has a roof 21, and the upstream end of the coating chamber is formed by an end wall 35, from which hangs a port 23, which leaves a space for the passage of the substrate 1 into the coating chamber through an input slot 31.

Upstream of the gate 23 there is an 8662904-29 pre-chamber 25, in which heating means 26 are provided. Such heating means may consist of radiant heaters, or one or more burners, while it is also possible, as shown, for a finned radiator 5 is used. A roof portion 27 hangs down from the roof 21 of the passage and the wall 22 at the upstream end of the coating chamber and forms a roof of the pre-chamber 25, which slopes down towards the entrance slot 24 towards the coating chamber.

During operation, a semi-natural gas flow from the pre-chamber 25 will be drawn into the upstream end of the coating chamber 6, so that the gaseous environment in the immediate vicinity of the top surface of the substrate 1 is at least in the zone where the formation of the coating is controlled by pre-heated gas, which is fed downstream 3 into the chamber 6, to enter this chamber in contact with the substrate 1 and to form a coating layer which, at least as far as the contact zone with the coating prep-20 cursor material extends, the substrate is covered.

The effect of the end wall 22 and the port 23 is to control the height of the flow of atmospheric material flowing from the upstream direction into the coating chamber 6 and forming the covering layer covering the belt so that the atmospheric conditions in that area where coating formation begins can be controlled more easily.

EXAMPLE I

In a specific practical embodiment of the device shown in Figure 1, the coating chamber 6 has a width of slightly more than -3 meters, in order to be suitable for glass tapes with a width of up to about 3 meters. The roof structure 5 above the spraying zone 9 of the coating chamber is located just 1 meter above the level of the belt web 1 and the spray nozzle of the drop dispensing nozzle 7 is close to the level of this roof. This nozzle 7 can deliver a conical flow of drops in a direction S at an angle of 45 ° to the horizontal 8602904-30. The bridge wall 14 at the downstream end of the spraying zone 9 is located at a distance of 2.2 meters from the upstream end wall 22 of the coating chamber. The passage 13 has a height which decreases from 5 cm at the location of the outlet slot 15 to 25 cm at the location of its downstream end. The length of the passage is 4.5 meters.

This device is especially designed for forming tin oxide coatings, starting from a solution of stannous chloride as a coating precursor material.

In the use of such a device, a tin oxide coating with a thickness of 750 nm was formed on a 6 mm thick glass tape, moving at a speed of 8.5 meters per minute. The glass entered the coating chamber at a temperature of 600 ° C and the coating precursor used was an aqueous solution of stannous chloride with ammonium bifluoride to apply dope ions to the coating. This solution was sprayed from the nozzle at a rate of 220 liters per hour, while the nozzle was moved back and forth across the belt path.

Radiant heaters in the roof of the spraying zone were turned on and air was released through the mouth 12 at a rate of 6000 Nm3 / min and a temperature of 400 ° C. As a result, a portion of the sprayed stream of coating precursor material had evaporated, leaving only a portion that collided with the glass.

The coating precursor vapor thus formed was entrained in the preheated air stream released through the mouth 12 and flowed through the exhaust slot 15 and through the passage 13 to the exhaust pipes. Therefore, this example also makes use of the invention, which is described in British patent application 85.31423.

Suction forces 35 were generated in the exhaust pipes 16, 19 in order to extract about 100,000 m3 / hour of atmospheric material from the coating chamber with an average temperature of about 350 ° C, thus creating a covering layer of gas, which was heated by the heating 8602904 - member 26 and which covered the substrate was sucked in. Such preheating was accomplished by heating a finned radiator to a very high temperature.

In addition, the side aspirators 19 draw in atmospheric material from the bottom of the level of the belt, thereby preventing mixing of atmospheric material between the zones vertically above and vertically below the belt web.

It was found that this allowed an extremely fine control of the atmosphere immediately above the substrate in the area where coating formation began. This proved particularly advantageous in providing a regular coating of the required thickness, while increasing the width of the belt over which the coating of this required thickness was formed.

As a result, the formed coating had a fine crystal structure at the glass / coating interface, which promoted a uniform, high quality coating structure and therefore also yielded good optical qualities, while avoiding the inclusion of coating reaction products, which would lead to errors.

FIGURE 2

In Figure 2, parts having the same functions as in Figure 1 have corresponding reference numerals.

In the spray zone 9 at the upstream end of the coating chamber 6, the heating members 10 and the gas delivery pipe 11 are absent. A gas delivery conduit 27, which has a delivery slot 28 that extends the entire width of the coating chamber, is provided to deliver additional vapor phase coating precursor material which is entrained in the trickle stream.

Downstream of the outlet slot 15 under the bridge wall 14, the roof structure 5 continues to form a passage 13 of the coating chamber 6, which again has a decreasing height.

The roof 5 of the passage 13 consists of a porous construction and is covered by a chamber 29, which can be filled via the pipe 30 with pre-heated air, in order to introduce such heated air through the roof of the passage 13. and to form a barrier layer against corrosion of the roof there and against condensation of the coating precursor vapor on the roof.

Baffles 31 are provided along the length of the passage 13 on either side of the coating chamber, which project inwardly from the side walls of the coating chamber over the edges of the substrate 1. These baffles extend the entire length of the substrate web occupied by the passageway and indeed these baffles extend the entire distance upstream of the upstream end of the pre-chamber 25, only 15 at the location of the area where they would collect the sprayed stream 8 of the coating precursor material have been interrupted.

Under the upstream end 22 of the coating chamber 6, the vertical port 23 shown in Figure 1 has been replaced by a pivotable port 32, which allows a variable input slot 31, so that the rate at which atmospheric material from the pre-chamber 33 enters the coating chamber. can be aspirated, to form a coating for covering the glass, can be more easily controlled. In addition, a gas delivery pipe 33 is provided for discharging preheated gas down into the antechamber to form the layer of atmospheric material immediately above the substrate 1 to at least the zone where the flow of coating material collides with the glass. The upstream end of the pre-chamber is at least substantially closed by a boundary wall 34.

A means 35 is provided for delivering gas into the vicinity of the substrate 1 to form a continuous flow flowing downstream 3 below each edge of the substrate web 1 and over at least a portion of the web length which is occupied by the coating chamber 6.

The gas dispenser 35 under the belt includes four 8602904-33 distribution spaces 36, which are positioned two by two and extend at least substantially the entire width of the coating station 4. In the top of each distribution space 36, a slot 37 is formed, which is bounded by a deflection lip 38, so that gas injected through the slots 37 is directed in the downstream direction 3 past the coating station 4. The slots 37 extend the entire length of each distribution space 36 transversely of the coating station 4. If desired, such slots can be replaced by a plurality of spaced-apart mouths. As shown in Figure 2, a deflection plate 39 is positioned above the distribution spaces 36 so that the injected gas is not delivered directly adjacent to the substrate 1. The distribution spaces 36 can be supplied with preheated gas from both sides of the coating station 4, e.g. from heat exchangers. As the released gas, air can be used and it can be easily heated, by heat exchange with incinerator combustion gases. Such a gas is preferably preheated to a temperature within 50 ° C of the temperature of the substrate when it enters the coating chamber 6. Gas released below the substrate 1 may be removed from the vicinity of the substrate 1 by an optional exhaust pipe 40, the inlet of which may extend transversely below the substrate web, eg in accordance with the outlet inlet 17 located above the web.

In the vicinity of the upstream end of the coating chamber, an auxiliary gas delivery conduit 41 is provided just above the level of the substrate for delivering preheated gas into the chamber adjacent to the substrate, to flow in the downstream direction and to cover the layer which is behind the port 32 is supplied to the coating chamber to enhance and further condition the atmosphere in contact with the substrate where it first contacts the coating precursor material.

EXAMPLE II

The apparatus of Figure 2 was used to form a tin oxide coating of the same thickness as in Example 1 on a glass of the same thickness and moving at the same speed 8602904 I 1 - 34 -. The coating precursor material used consisted of stannous chloride dissolved in dimethylformamide and delivered through a spray nozzle 7 placed 75 cm above the belt and angled 30 ° horizontally. Stannous chloride vapor was released from the slot 28. The vapors formed in the spray zone 9 were drawn through the passage 13 by a frontal suction, only from the exhaust pipe 16 / at a speed in order to obtain a coating of the desired thickness.

The glass entered the coating chamber 6 at a temperature of 600 ° C, while preheated air at a rate of 3000 Nm3 / hour was released into the pre-chamber 25 from the pipe 33 at a rate of 3000 Nm3 and as a coating layer which covered the glass flowed into the coating chamber 15.

The atmospheric material in the spray zone 9 was intimately mixed and a continuous flow of vaporized atmosphere was contacted through the passage 13 with the surface of the substrate on which the coating 20 was formed.

Preheated air up to a temperature of 550 ° C was delivered at a rate of 3000 Nm3 / hour from the dispenser 35 below the substrate web.

This also provided excellent results regarding the width of the formed coating of uniformly high quality.

FIGURES 3 AND 4

In Figures 3 and 4, parts have the same functions as those. which are shown in Figures 30 1 and 2 again the same reference numerals.

In the embodiment of Figures 3 and 4, the roof structure 5 above the passage 13 has a horizontal course, so that the passage has a uniform height over its entire length, namely the height of the outlet slot 15.

At the downstream end of the passage 13, the exhaust pipe 16 is absent and the downstream end of the passage is at least substantially closed by a boundary wall 42 instead of the outlet vane 8602904 18.

- 35 -

The pre-chamber 25 is separated from the coating chamber 6 by a fence wall 43, which hangs down from the roof 21 thereof, and the fence wall 5, in turn, supports a vertically movable gate 44, which may be composed of a number of sections across the width of the coating chamber 6, to allow differential opening of the inlet slot 24. As shown in Figure 4, the bottom corners of port 44 are cut away, such as at location 45, to allow increased volume flow of the gas to the sides of the coating chamber, and valves 46 are used to control the opening at the location of these bottom corners.

Fans are provided under the pre-chamber 25 for blowing pre-heated air up past the edges of the path of the substrate 1, while a further fan 48 is provided to blow pre-heated air in the pre-chamber from an upstream direction, between the upstream shielding wall 34 and the substrate 20 1.

In the pre-chamber heating elements 49, eg burners, are arranged and as shown in figure 4, these heating elements are placed in such a way that they emit more heat at the sides of the pre-chamber than at the center thereof.

EXAMPLE III

The apparatus of Figures 3 and 4 was used to form a 400 nm thick fluoropope tin oxide coating on a 5 mm thick float glass belt traveling at a speed of 8.5 meters per minute and the coatings chamber entered with a temperature of 600 ° C.

The coating precursor used consisted of a solution of tin chloride with ammonium bifluoride for applying dope ions to the coating. This solution was sprayed from the nozzle at a rate of 120 liters per hour under a pressure of 23 bar, while the nozzle was reciprocated at a rate of 23 strokes per minute.

8602904, λ - 36 -

Preheated air up to a temperature of 600 ° C was released from the fans 47 and 48 into the pre-chamber 25 and then sucked into the coating chamber to form a coating covering the glass. The extraction above the level of the substrate took place at a rate of 60,000 m3 / hour and at a temperature of about 350 ° C, in order to maintain a generally downstream flow of material within the coating chamber.

Radiant heaters 10 installed in the roof were turned on to evaporate the sprayed coating precursor material during its movement toward the substrate. Due to the turbulence caused by the back-and-forth movement of the spray nozzle and the sprayed flow of the coating precursor material, the evaporated material was intimately mixed with air in the spray zone 9 and this vaporized atmosphere was introduced into the exit slot 15 and through the passage 13 sucked. The coating precursor vapor mixed with the coating of atmosphere, which was in contact with the glass, and a coating of the required thickness was deposited. Therefore, this example also uses the invention, which is described in British patent application 85.31424.

Preheated air up to a temperature of 550 ° C was released from the dispenser 35 below the substrate web at a rate of 3000 Nm3 / hour.

The pre-chamber 25 included burners 49 for preheating the atmosphere. These burners allow the air to be heated according to any desired temperature profile, eg to a higher temperature at the sides of the pre-chamber.

The coating formed by the method of this example had an extremely high quality and uniformity over at least almost the entire width of the belt.

EXAMPLES IV TO VI

In a variant of each of the previous examples, the device is used to apply a coating to glass which has been cut into plates and then reheated, the procedures otherwise being similar.

Corresponding results regarding the coating quality were achieved.

The invention is not limited to the embodiments described above, which can be varied in many ways within the scope of the invention.

10 8602904

Claims (42)

1. Pyrolytic coating method, in which a hot glass substrate in sheet or hand form moves in a downstream direction under a coating chamber which is opened down to the substrate and in which a coating of a coating precursor material is formed on the surface of the substrate, characterized in that the gaseous environment in the immediate vicinity of the surface of the substrate, at least in the zone where such coating formation begins, is controlled by introducing preheated gas downstream into the chamber to enter the chamber in contact with the substrate and to form a coating layer covering the substrate at least as far as this zone. A method according to claim 1, characterized in that a generally downstream flow of gas through the coating chamber is maintained at least in part by aspirating atmospheric material from this chamber at its downstream end. Method according to claim 1 or 2, characterized in that the coating chamber is at least substantially closed at its downstream end, in order to prevent an exchange of atmospheric material between the downstream end of the coating chamber and a further downstream region of the substrate web. obstruct . 4. A method according to claim 3, characterized in that the glass substrate comprises a properly formed hot glass strip, the coating being formed after the strip exits a strip former and before it enters a softening lehr. A method according to any one of the preceding claims, characterized in that a flow of atmospheric material beyond the side edges of the substrate and between zones vertically above and vertically below the substrate is prevented over at least a part of the length of the coating chamber. 8602904 - 39 - Method according to any one of the preceding claims, characterized in that a coating pre-cursor solution is sprayed downwards and downstream. A method according to any one of the preceding claims, characterized in that a coating pre-cursor solution is sprayed down into the coating chamber and through the coating layer. 8. A method according to claim 7, characterized in that the solution is sprayed with sufficient energy to ensure a clear contact between the remaining sprayed coating precursor material and the substrate, in order to start the coating of the substrate surface, the atmosphere being provided of coating precursor material in the vapor phase, is directed downstream from the spraying zone along and in contact with the coated substrate surface for a contact time of at least 10 seconds, after which any residual material from the precursor flow away from the sub -20 street is headed. 9. A method according to any one of claims 1 to 6 for forming a metal oxide coating, characterized in that coating precursor material and an oxidizing gas are continuously fed into a mixing zone, wherein the precursor material and the oxidizing gas are brought together out of contact with the substrate and where they are subjected to rng forces to form an atmosphere containing an intimate mixture of precursor vapor and oxidizing gas, a flow of such mixture being continuously fed from this mixing zone into and along a passage, at which substrate surface is exposed. Method according to any one of the preceding claims, characterized in that the gas forming the coating layer is preheated to a greater degree than is possible by heat transfer only from the substrate. A method according to any one of the preceding claims, characterized in that the gas forming the side edge regions of the covering layer is preheated to a greater extent than at the center. A method according to any one of the preceding claims, characterized in that the gas of the coating layer is heated at least above the side edges of the substrate 5 to a temperature which is greater than that of the underlying edge regions of the substrate. 13. A method according to any one of the preceding claims, characterized in that the gas for forming the coating layer enters the upstream end of the coating chamber from an adjacent pre-chamber. Method according to claim 13, characterized in that the preheating of the gas is carried out at least partly in the pre-chamber and from above the level of the substrate. Method according to claim 14, characterized in that the preheating of the gas in the pre-chamber is effected by means of burners. A method according to any one of claims 13 to 2015, characterized in that the preheated gas is blown upwards from below the level of the substrate to the sides of the pre-chamber. Method according to any one of claims 13 to 16, characterized in that the preheated gas is blown downstream of the substrate in the antechamber from above the level of the substrate. 18. A method according to any one of claims 13 to 17, characterized in that the preheated gas is blown down into the pre-chamber and this gas is prevented from flowing down the side edges of the substrate. 19. A method according to any one of the preceding claims, characterized in that the volume flow of the gas forming the covering layer is controlled differentially over the width of the substrate. 20. A method according to any one of the preceding claims, characterized in that atmospheric material is maintained in a generally downstream flow over a substantial part of the height of the chamber, partly by a gas flow in direct the chamber downstream. 21. A method according to any one of the preceding claims, characterized in that at least one auxiliary stream of preheated gas is introduced into the coating chamber to flow in or downstream of the coating layer and through the zone where coating formation begins. 22. Device for pyrolytically forming a metal compound coating on a surface of a hot glass substrate in plate or hand form, with a conveying means for transporting said substrate along a track in a downstream direction, a roof structure, which comprises a coating chamber which opens downwardly to the web and forms a precursor coating material dispenser in the chamber, characterized in that a pre-chamber is arranged upstream of the coating chamber, which communicates with the coating chamber via an entrance slot, which is partially defined by the path of the substrate and through which gas can flow into the coating chamber to form (when the device is in operation) a coating layer covering the surface of the substrate along a first portion of the length of this chamber and that a means is provided for controllably preheating the gas constituting the coating layer . 23. Device according to claim 22, characterized in that exhaust pipes are arranged with one or more inlets at the downstream end of the coating chamber. 24. Device according to claim 22 or 23, characterized in that a boundary wall is arranged above the substrate web, which extends over the entire width of the downstream end of the coating chamber and at least substantially closes it. 25. Device according to any one of claims 22 to 24, characterized in that the coating station is arranged between the exit of a tape-making device and the entrance to a water softener. 26. Device as claimed in any of the claims 22 to 25, characterized in that an element is arranged over at least a part of the length of the coating chamber for preventing a flow of atmospheric material beyond the sides of the substrate web and between zones vertically above and vertically below this track. An apparatus according to any one of claims 22 to 26, characterized in that the coating precursor material dispenser 10 is positioned such that liquid coating precursor material is sprayed down and downstream. 28. Device according to claim 27, characterized in that the spraying means is arranged to spray the coating precursor solution in a spraying zone of the coating chamber from a height above the substrate web of at least 75 cm, which is arranged for heating the supplying heat to the spraying zone, the roof structure forming a passage portion of the coating chamber 20, which leads downstream of this spraying zone and provides the coating chamber with a total length of at least 2 meters, while a means is provided for generating extraction forces on atmospheric material within such a passageway, to cause such material to flow along the substrate web to the downstream end of the passageway and to enter an exhaust pipe to carry such material away from the substrate web. Device according to any one of claims 22 to 27, characterized in that the coating chamber 30 has a passage through which coating precursor vapor and an oxidizing gas can be passed downstream in contact with an upper substrate surface during the transport of the substrate and in which an element is present which defines a mixing zone in which the coating precursor material 35 and the oxidizing gas can be combined and in contact with the substrate to be mixed to form an atmosphere comprising an intimate mixture of the precursor vapor and the oxidizing gas which mixing zone communicates with the passage 8602904-43 to allow a flow of such mixture to flow through the passage from the mixing zone. Device according to any one of claims 22 to 5 29, characterized in that the roof structure in the downstream direction has a marked height reduction above the substrate web, so that the downstream flow of atmospheric material from the release zone of the coating precursor material into the coating chamber is throttled. An apparatus according to any one of claims 22 to 30, characterized in that the gas preheater is controllable in such a way that it heats the different gaseous parts of the coating layer over the width of the substrate web to different degrees. An apparatus according to claim 31, characterized in that the gas preheater is controllable such that it heats the gas-forming side edge regions of the coating layer to a greater degree than the gas-forming central portions of the layer. Device according to any one of claims 22 to 33, characterized in that the partition above the entrance slot has a gate for adjusting the opening of the entrance slot. 34. Device as claimed in claim 33, characterized in that the gate is provided with independently movable sections for adjusting the input slot differential over the width of the substrate web. 35. An apparatus according to any one of claims 22 to 34, characterized in that a means is provided for heating the atmosphere in the pre-chamber from above the level of the substrate web. An apparatus according to claim 35, characterized in that said pre-chamber heater comprises burners. An apparatus according to any one of claims 22 to 36, characterized in that a means is provided for blowing pre-heated gas from below the level of the substrate web up to the sides of the pre-chamber. 8602904 V »♦ · '- 44 - 38. Device according to any one of claims 22 to 37, characterized in that a means is provided for blowing preheated gas from above the level of the substrate web in the downstream direction into the pre-chamber. 39. An apparatus according to any one of claims 22 to 38, characterized in that a means is provided for blowing preheated gas down into the antechamber and preventing said gas from flowing down the side edges 10 of the substrate web. 40. Device according to any one of claims 22 to 39, characterized in that the pre-chamber has a roof which slopes downwards towards the top of the entrance slot. An apparatus according to any one of claims 22 to 40, characterized in that a means is provided for directing a gas stream downstream into the chamber. in order to maintain a generally downstream flow of atmospheric material over a substantial portion of the height of the chamber. 42. An apparatus according to any one of claims 22 to 41, characterized in that a means is provided for delivering into the coating chamber at least one auxiliary stream of preheated gas to flow in or adjacent the coating layer in the downstream direction, as well as through the zone where the formation of the coating begins. 30 8602904